Multicolor anodizing of aluminum



Dec. 6, 1966 N, E. DUNNING 3,290,232

MULTICOLOR ANODIZING OF ALUMINUM Filed Sept. 17, 1964 5 Sheets-Sheet l 3 lll/lll L A "A 1 g A1203 UNSEALED 7 .mwgggl p AI (0l-I)5 SEALED Al NICKEL ACETATE- H20 BLUE G YJ- O\ AL(0H235EALED y/ /R/EW/y/v /7 NICKEL ACETATE INVENTOR.

20G-212 F /Voe/ .Dunn/n ATTORNEY.

N. a DUNNING 3,290,232

Dec. 6, 1966 Filed Sept. 17, 1964 WATERPROOF COVER AIZO`3 msi/[MD Z9 RED DYE 1N H30 ISO-ICIO'F LLOW\[`CLE/\R \[\RED /I /l F 27 M203 UNSEALED ATTORNEY Dc. 6, 1966 N. E. DUNNING MULTICOLOR ANODIZING OF ALUMINUM 5 Sheets-Sheet 5 Filed Sept. 17, 1964 United States Patent O 3,290,232 MULTICOLOR ANODIZING F ALUMINUM Noel E. Dunning, Charlotte, Mich., assignor to Austin A. Webb, Kalamazoo, Mich. Filed Sept. 17, 1964, Ser. No. 397,332

34 Claims. (Cl. 20a-35) s This application is a continuation-in-part of the copending application, now abandoned, Serial No. 845,203, tiled October 8, 1959, for Process of Coloring Aluminum with Multi-Color Designs, by Noel E. Dunning.-

The invention relates to an improved method and materials for multi-color anodizing of aluminum.`

The principal objects of this invention are:

First, to provide an' improved process for the application of multicolor designs to anodized aluminum surfacesJ and the sealing ofthe anodized surface with the colors trapped therein in a more rapid and inexpensive manner than was heretofore possible.

Second, to provide a process for multicolor anodizing aluminum that transfers more color into the aluminum from the dye carrying vehicle in a shorter time and with less `expensive materials.

Third, to provide an improved process of multicolor anodizing aluminum from preprinted transfer sheets that can be carried out Withfewer steps and at less time and expense than prior processes.

Fourth, to provide a processofV multicolor anodizing in which a dark color is applied over a lighter color prior to sealing the anodized surface thus reducing the cost of producing a design of a dark col-or on a backgroundofa lighter color.

Fifth, to provide an improved method of color transfer from a color carrier to the pores of anodized aluminum by application'of the colored carrier to a heated surface so that more colors may be applied to the surface in less v time and at less expense.

does not require the use of expensive solvents for removing excess inks and coatings from the colored aluminum.

Eighth, to provide 'a process which permits blending of two or more colors to form a new color in the surface of the aluminum from blended basic colors.

Ninth, to provide a process for coloring aluminum which accelerates the transfer of color or dye from a carrier medium into the metal by subjecting the carrier medium to water or other solvent for the dye while in contact with the metal.

Tenth, to provide a process for accelerated and accurately delineated transfer of colors or dyes from adjacently applied quantities of color carrier mediums into the pores of the metal to which the mediums are applied which consists of protecting the 'coloring mediums on the metal by means of a protective material applied over the carrier medium or incorporated directly in the lcarrier medium, which protective medium is relatively insoluble in water at elevated temperatures or other solvent for the dyes but which is pervious or permeable to the water or solvent so that when the metal with the protected carrier medium applied thereto is subjected to the dye solvent the solvent will penetrate the protective medium and effect rapid but localized transfer of the dyes to the metal while physically holding the carrier mediums in their applied positions to prevent accidental or undesired transfer of colors or dyes to unselected portions of the metal.

Eleventh, to provide, as products for the accomplishment of the processes, color carriers incorporating suitable protective mediums having the properties described in paragraph seven above, and design transfer sheets having protective layers incorporated therein and embodying the same protective properties.

Other-objects and advantages of the invention will be apparent from a consideration of the following description and claims. The drawings, of which there are three sheets, illustrate several modified forms of the multicolor anodizing process of the invention and several examples of the design transfer sheets and dye vehicle or carrier pastes usable in some forms of the process.

FIG. l is a fragmentary cross sectional view conventionally illustrating an aluminum surface printed with a multicolor design and prepared for transfer of the color design into the surface of the aluminum.

FIG. 2 conventionally illustrates the step of transferring the color from the printing in FIG. 1 into the surface of the aluminum.

FIG. 3 conventionally illustrates the sealing of the color design into the surface of the aluminum and removal of the coloring and protective coating used to apply the design.

FIGS. 4 to 7 illustrate a modified form of the coloring process and in FIG. 4 there is conventionally illustrated a preprinted transfer sheet having a multicolor design applied thereto. Y

FIG. 5 conventionally illustrates the mechanical applition of the transfer sheet shown in FIG. 4 to the surface of a piece of aluminum.

FIG. 6 conventionally illustrates the removal of the transfer sheet and the transfer of the color dye or media from the transfer sheet into the surface of the aluminum.

FIG. 7 conventionally illustrates the sealing of the dye into the surface of the aluminum and the removal of excess dye paste therefrom.

FIGS. 8 to l1 illustrate a third modified form of the process and in FIG. 8 there is conventionally illustrated a preprinted transfer sheet with a methylcellulose ycoating and a multicolor design applied thereto.

FIG. 9 conventionally illustrates the transfer sheet and design of FIG. 8` appliedl to an aluminum surface and protected by a waterproof coating and subject to a color bath for coloring unprotected parts of the surface of th aluminum.

FIG. l0 illustrates the steps of removing the transfer sheet and causing transfer of color tothe printed portions of the plate.

FIG. l1 conventionally illustrates the step of sealing the color into the surface of the aluminum'.

FIGS. 12 to 15 illustrate a fourth variation lof the Icolor process with FIG. l2 conventionally illustrating a multicolor design printed on the surface `of the aluminum with a special type of dye paste.

FIG. 13 -conventionally illustrates the step of transferring the color or dye from the paste in FIG. 12 to the surface of the aluminum.

FIG. 14 conventionally illustrates the step of sealing the colored surfa-ce of the aluminum shown in FIG. 13.

FIG. l5 illustrates the step of removing the paste or ink from which the dye has been extracted.

FIG. 16 is a schematic view conventionally illustrating another form of the process using direct color application to the anodizing aluminum.

FIGS. 17 to 22 conventionally illustrate another form of the process using preprinted decal or transfer sheets, with FIG. 17 illustrating the preprinted transfer sheet.

FIG. 18 illustrates the step of applying the transfer sheet to the anodized aluminum.

FIG. 19 illustrates the manner of separating the backing portion of the transfer sheet from the transferred design and the metal.

FIG. 20 illustrates the step of transferring the color fromits carrier to the metal.

FIG. 21 illustrates the step of removing the depleted color carrier.

FIG. 22 illustrates the step of sealing the porous colored surface of the aluminum.

FIG. 23 illustrates a further modification of the method in which the color bearing pastes a-re applied directly to the metal and the metal and pastes heated in a chamber.

FIG. 24 illustrates a further step after FIG. 23 in which saturated steam is admitted to the heated pastes to transfer the color.

Prior art The process of coloring the surface of aluminum with one or more colors is well known and Patent No. 2,614,- 912 to Rice is listed as an example of such prior coloring processes. As is indicated in that .patent it is well known that aluminum surfaces can be anodized to provide a relatively thick coating of porous aluminum oxide which will assume or absorb the color from dyes and inks applied thereto. After the color has been absorbed into the anodized surface, the surface can be sealed by dipping the aluminum in a bath of hot water between 200 and 212 F. and this sealing process so closes the pores of the aluminum oxide coating that the color is trapped within the metal surface. The surface will not give up the color to ordinary washing or wiping actions nor will it absorb and hold any additional colors applied thereto after the surface is sealed.

Rice, generally, applies inks containing a coloring matter (and in some cases a noncoloring matter) that is acceptable to the anodized -aluminium surface, mixed in the liquid vehicle of the ink, to the metal surface. He then removes the vehicle while fixing the color (and any noncolor) matter in the surface. He discloses that organic dyes such as direct dye stuffs, acidic dyestuffs, basic dyestuffs and mordant colors which are soluble in water, alcohol or oil, are mixed as inks in their appropriate solvents with film forming liquids that also go into solution with the solvents for the dyes. Oily printing inks are mentioned as suitable vehicles for `oil soluble dyes, and alcohol soluble lacquers such as used in the printing trade are used as vehicles for alcohol soluble dyes.

The example given by Rice apply a lacquer 4base ink containing a dye, yboth soluble in ethyl alcohol, Carbitol or other lacquer solvent. The ink is permitted to set for from to 60 minutes for each color to dry before applying a second color. The work is then washed with the solvent and the metal sealed in hot water.

In another example, Rice uses a water soluble basic dye ink for. one color. The second color is apparently a zein base ink dissolved in water and Carbitol. The inks are dried separately and the visicosities of the two inks are adjusted so that one does not dissolve or bleed into the other. Rice uses the vehicle of one ink as a barrier for the second. While not mentioned, the dried inks are apparently washed off with suitable solvents and the metal sealed.

A third example of Rice uses alcohol or oil soluble dyes and ink to form a design, with drying of each color separately. A colorless barrier or resist of hard asphaltum is applied to other areas of the metal and the sheet is dipped in water containing a third dye. The metal is then washed successively in mineral spirits and solvents for the inks and sealed in hot water.

Rice disclosed that compatible ink vehicle solids, solvents and dyes include ethyl cellulose, vinyl chloride, cellulose nitrate, zein or oily ink varnishes. Zein is dissolved by mixture of water and Carbit-ol, nitrocellulose by its usual solvents, and oily inks by mineral spirits. A wide variety of suitable dyes are listed.

Sobol, in Patent No. 2,778,790 followed Rice in disclosing the use of inks of special composition that include dyes and vehicles that are insoluble in water but permeable by water. By way of example he used an oil soluble dye with ethyl cellulose or cellulose nitrate as a vehicle. The inks were prepared in a consistency that would not flow and were printed, screened or applied and dried separately. The printed surface was then placed in hot water sto that the hot water penetrated the water permeable veh1cle to seal dyes in the surface of the metal and also seal the uncolored areas of the metal. The degraded ink vehicle and carrier was then washed from the metal with trichlor ethylene as a solvent. n

An indicated in the foregoing objects, this invention provides improved steps which permit the economical ap- A plication of the colors of these old processes to the surface of anodized aluminum in more sharply defined and mixed or blended multicolor designs. As used herein, the term anodized is intended to imply an aluminum surface which has been treated to provide the relatively thick and porous oxide coating referred to above. When referred to as unsealed this anodized coating is in its open porous state and when sealed the coating is no longer capable of absorbing further or different dyes. It will be understood that throughout the several forms of the process to be described the materials and surfaces should be kept as clean and free from foreign materials as possible in orde-r to obtain the brightest reproduction of the designs in the surface of the aluminum.

In FIGS. 1 and 2 the sheet or body of aluminum 1 has its surface treated as at 2 by anodizing to provide the previously described and well known porous aluminum oxide coating. To this coating is rst applied a layer of a dye paste 3 in any predetermined outline or design pattern and in any selected color such as the red indicated. This first pattern 3 is permitted to dry by natural air circulation or by forced hot air heat. A second design pattern such as the blue dye paste 4 may then be applied to the surface with adjacent portions of red and blue pastes overlapping if desired. The color patterns 3 and 4 may be applied in any convenient fashi-on such as by silk screen stencils or gravure printing from plates or cylinders. The reason for drying the first color pattern 3 prior to application of the second pattern is to prevent smearing of the wet dye paste of one color onto the screen or plate which applies the second color. After the several color designs 3 and 4 have been applied to the surface, a protective coating 5 of an uncolored paste or lacquer is applied over the printed designs and any unprinted exposed area of the anodized surface. The extension of the protective coating 5 to the unprinted areas of the surface is desired to protect the bare metal from stray coloring which may reach it from adjacent areas 'but as will -be pointed out very little dye strays from its deposited position.

The dye pastes 3 and 4 and the protective coating 5 `are prepared in the following manner. A solution of a water soluble gum such as gum tragacanth or water soluble starch or plastic is prepared in a relatively thick solution of from 6% to 10% of the gum or solid. The gums, starches or plastic are slowly soluble in cold water and swell and form pastes in hot water. To this solution may be added a dye solvent such as propylene glycol methyl ether. Other solvents such as glycerin or urea and wetting agents may be added which are capable of dissolving the particular dye to be used. The solvent permits more dye to be absorbed into the gum for more intense colors. The mixture of the water-gum solution dispersed in the solvent is thoroughly mixed and desirably cooked for six hours.

The selected dye which `is soluble in water and, or the solvent of the gum mixture is next mixed into the paste and the pH or acidity of the mixture is desirably adjusted using acetic acid or other acid with a pH value of between 5 `and 6.5 being suiicient for most dyes. The consistency of the dye, gum and solvent mixture is adjusted to suit the type of printing to be used and the color designs are printed as previously described.

The protective coating 5 consists of the uncolored gum solution and solvent mixture described above. Alternatively, a plastic, glue, lacquer or gelatin that is only 15 into the anodized surface of the metal.

. S slowly soluble in water or the solvent for the dye being used can be substituted for the gum paste.

The aluminum with the printed and protected surface is next placed in a bath 6 of Water or solvent for the dye as indicated in FIG. 2. The water will absorb through the protective coating and the gum in the dye pastes 3 and 4 to assist the water and solvent already present in the dye paste in causing the transfer or migration of the color dyes from the dye pastes into the aluminum oxide coating 2 as indicated at 7 and 8. The transfer of the color from the dye paste to the metal is speeded up and intensified if the bath 6 is heated to between 130 and 190 F. but the bath must not be heated to a much higher temperature as it would then start to seal off the porous surface of the aluminum oxide.

After the color has been transferred to the areas 7 and 8 which takes about 5 to 30 minutes in a hot bath, the sheet of aluminum 1 is transferred to a sealing bath of hotter water as indicated at 9 in FIG. 3. A bath of from'200 to 212 F. is effective in sealing the porous surface of the aluminum oxide as indicated at 10. The action is facilitated by the addition of nickel acetate to the bath. The protective gum coating 5 and the residue of the dye pastes 3 and 4 is washed away or may be wiped away in the bath 9 without resorting to expensive solvents.

The example of the process shown in FIGS. 4 to 7 is particularly applicable to irregular surfaces in that the transfer sheet can be applied over -a curved surface more easily than fa printing plate or roll but for the pur- -pose of description, the process is described with ref- 'erence to a flat surface. A sheet of decal paper 11 precoated with a quick soluble glue 12 such a dextrin is first given :a coating 13 of a gum or paste such as the protective coating 5 of FIGS. 1 to 3. The selected design is then printed or screened onto the surface 13 as by the blue dye paste 14 and the yellowdye paste 15 and it is pointed out that substantial overlapping of the different colors may be provided if desired as at 16. As in the first form of the process, each coating of dye paste is dried to prevent smearing lof the printing element. The drying may be forced by the application of heat between successive printings.

The transfer sheets 11 with the preprinted color designs can be stored and shipped and handled almost at will to be applied to the surface of the aluminum sheet 17 and its anodized unsealed oxide coating 18` as shown in FIG. 5. By wetting the surface 18 or the printed coating 14-16, or both, with clear paste 19 the transfer sheet will adhere to the metal and can be accurately registered thereon. The metal with the transfer sheet adhered thereto is then placed in a tank or bath 20 of a solvent for the dyes in the dye pastes. As in FIG. 2 this bath may be water and is desirably heated to between 130 and 190 F. The water absorbs quickly through the transfer sheet 11 to the quickly soluble glue 12 allowing the sheet 11 to be removed in 5 to 10 seconds. Removing the paper prevents the dyes from being absorbed into the paper and continued immersion for from 5 to 30 minutes causes the dye to migrate from the printed areas 14 and It is pointed out that where the printed areas overlap on the transfer sheet, the colors mix or blend during transfer to provide a third `color area such as the green area 50 in the surface of the metal. The colored metal with the residue of the dye pastes is removed from the bath 20 and the anodized surface is sealed by immersion in a hot sealing bath 21 as indicated conventionally in FIG. 7. Residue of the dye paste may be removed in the bath or later.

FIGS. 8 to 10 illustrate another variation of the coloring process. As is shown in FIG. 8 there is first porvided a sheet of paper 22 coated with a quickly water soluble glue 23. To this is applied a layer 24 of dry solidified methylcellulose which is held in place by the glue 23. This layer has the physical property of being soluble in cold water but relatively insoluble in hot water. At

temperatures ranging from 130 F. and upwards the layer will maintain its body in water but at room temperature or below F. it will dissolve in water. Upon this methylcellulose layer the desired design is printed in the selected colors indicated at 25 and 26 with overlapping of colors if desired at 27. To sharpen the contrast and detail of the picture, black may be employed as at 28. The dry transfer sheet can be handled and kept indefinitely.

When ready to be applied to the metal the transfer sheet 22 is applied, color side down, to the surface of the anodized aluminum 29. It is easily applied by wetting the metal and rolling on the sheet or by a thin layer of paste applied as in FIG. 5. If a background color is desired around the design on the transfer sheet, part of the metal is left uncovered as iat 30 and a waterproof protective cover 31 such as masking tape or a water insoluble spray is applied over the back ofthe transfer sheet and the metal with the protected sheet adhered thereto is immersed in a bath 32 of hot water as indicated in FIG. 9. The bath has a selected dye such as the red indicated dissolved therein and the unprotected area 3i) of the metal absorbs this color in a well known manner.

After the background red dye is absorbed the metal is removed from the bath 32 and the protective covering 31 is removed. The metal with the tranfer sheet still adhered thereto is immersed in -a second bath 33 of clear medium hot water as shown in FIG. 10. The water quickly dissolves the paste layer 23 and the paper is removed leaving the `dye pastes, protected |b`y the methylcellulose 24, in contact with the u-nsealed metal. The hot water does not dissolve the methylcellulose but passes through it to wet the dyes and effect color transfer to the metal in from 5 to 30 minutes. Where the colors overlapped at 27 a color blend is created at 34. The color 30 deposited by the first dip remains and any area protected by the waterproof cover 31 or the methylcellulose remains bright and clear. After the color transfer is complete the metal is transferred to a sealing bath 35 of very hot water and nickel acetate as shown in FIG. 11. The hot (200 to 212 F.) water does vnot dissolve the methylcellulose and both the cellulose and the dye residue can be removed after sealing the metal by flushing in cold water. y

FIGS. 12 to l5 illustrate a further modified form of the coloring process. In this process the dye pastes 36 and 37 are made up in different colors and include in addition to or in place of the gums or starches of the pastes referred to in connection with FIG. l, a variable percentage of a methylcellulose powder. This powder dissolves in the cool water in the dye paste but when the paste is applied to the aluminum oxide coating 38 and dried, the methylcellulose forms `a protective retaining body integral with the dye paste. The consistency of the paste is adjusted to the means of printing to be used. When methylcellulose alone .is used as a paste a viscosity of between 4000 and 8000 as represented by Dow Methocel MC4000 to 8000 sold by the Dow Chemical Co. is suitable. The printed aluminum body 39 with its printed anodized surface is then immersed in a bath 40 of hot water as shown in FIG. 13, to effect transfer of the dye from the paste to the aluminum oxide. The insoluble character of the methylcellulose in hot water prevents disintegration of the mass of dye paste in much the same manner as the methylcellulose coating in FIG. 8 so there is no bleeding or unintentional mixing of colors. The colored aluminum is sealed as shown in FIG. 14 by immersion in a bath 41 of hotter water containing nickel acetate. The jelled residue of the dye paste can be removed by light rubbing or by ushing with cool water as shown at 42 in FIG. 15.

All of the several forms of processes described are characterized by the use of a dye paste which is protected by a protective coating such as the clear paste coatings 5 and 13 in FIGS. 1 and 4, or the methylcellulose sheet 24 in FIG. 8 or the intermixed mass of methylcellulose in FIG. 12. The methylcellulose is a preferred species of the class of gums described. This protective coating is either insoluble or slowly soluble in the bath of liquid used to transfer the dye from the dye paste to the oxide coating. Since water is the cheapest transfer medium the protective coatings are desirably insoluble in water above 130 F. At the same time the coatings are water pervious and readily permit the passage of water to the dye paste to cause the transfer of the dye from the paste to the surface of the metal. The dye pastes are either soluble in water or contain a solvent which is readily dispersed in water. The relative insolubility of the protective coating permits the printing of various colors in close relationship without loss of detail caused by uncontrolled bleeding of the colors and with predetermined mixing of colors by overlapping the printed colors where desired.

FIGURE 16 shows a modified form of direct application of the color design to the unsealed anodized metal. A conveyor 43 having flights 44 for advancing sheets 45 of aluminum is conventionally illustrated. The sheets have at .least their upper surfaces anodized and in clean unsealed condition. In passing along the conveyor, the sheets 45 are first heated as by the resistance heating element 46 or radiant heat lamp 47, or both, to a temperature of between 150 and 210 F. Lesser heat reduces the effectiveness of the process and greater heat may cause irregular color deposit by creating steam in the dye pastes as will be described.

After being heated, the plates advance to a first color applying station 48 where a printing plate 49 applies a first color design 50. Continued heating is applied by the resistance element 51. The color paste, made as will be described dries almost immediately and the heated plate draws and absorbs practically all of the dye from the paste into the pores of the metal. A continued heating position to complete the drying and color transfer is indicated at 52. The sheet advances to a second color applying station 53. To illustrate a possible alternative color application, this station has a silk screen 54 with suitable masks 55 and a spray nozzle 56 for applying a second color paste 57. The second color is dried by the heated plate and at a second drying station 58.

The number, and type, of color applying stations may of course be multiplied as desired. After passing the nal color application and drier, the plate is deposited in a suitable sealing bath 59 of boiling water and nickel acetate. The depleted paste areas 50 and 57 may be removed in the bath or flushed off later with cold water or solvent as will be understood.

The color paste carriers 50 and 57 a-nd any uncolored barrier paste if such is used are made up of gum tragacanth, gum arabic, methylcellulose, starch or other wellknown Apaste forming materials which are soluble in water. Since the pastes are not subjected to external moisture until the color has been transferred, the rate or degree of solubility of the carrier has little effect on the printing and transfer process. Water soluble dyes of which several are well known are mixed i-n the color pastes. The addition of dye solvents and wetting agents to the paste will permit the absorption of additional dye for more intense coloring of the metal where desired. Examples of such solvents and wetting agents that are miscible in water and compatible with water soluble dyes are well known and some have been listed in connection with the first example of the invention. The heated character of the plate 45 cause the water soluble dye to transfer immediately from the paste to the pores of the metal as the paste dries.

A practical, and in some respects preferred form of the carrier paste for the pastes 50 and 57 is 75% distilled water, 25% leveling and dye solvent such as Dowanol PM maufactured by Dow Chemical Co.; thickener or paste body methylcellulose of the type and grade sold by Dow Chemical Co. under the trade name Methocel MC4000 or 8000. The thickener will ofcourse be used in the amount necessary for best application of the paste by the applying means selected. The dyes used are well known water soluble dyes commonly used for aluminum anodizing.

Further variations or modifications of the multicolor anodizing process is shown in FIGURES 17 and 24. In these related processes, dye carriers in the form of pastes impregnated with water soluble dyes are applied to the metal and the dye is transferred into the metal by the application of saturated steam. Again, since the dye pastes are not subjected to the action of a liquid, the solu-bility of the paste is of minor importance but again lmethylcellulose is preferred.

In FIG. 17 a transfer sheet 60 which may be metal foil, illustrated, or plastic or paper is coated with a separator layer of quick soluble adhesive 61 such as gum arabic. The several colored pastes of the designs 62, 63 and 64 are applied to the dextrin coating as in FIG. 8. The dyes are water soluble. No over or protective coating is added.

The transfer sheet is applied to the anodized surface of aluminum sheet 65 as in FIG. 18 by wetting the metal surface or applying a strip of clear paste 66 along one edge of the metal and rolling the transfer sheet onto the metal in a single firm rolling operation by the roller 67. The water or the water in the paste sticks the dye colored pastes to the metal and soaks quickly through the pastes to dissolve the gum arabic and the transfer sheet is removed as in FIG. 19. The metal sheet with the color pastes adhered thereto is placed in a steam chest 68 as in FIG. 20 and subjected to saturated steam for from l0 to l5 minutes. The moisture and heat of the steam combined with the moisture from the paste 66 transfers the dye accurately from the pastes to the pores of the metal. The color denuded paste 69 is flushed from the sealed metal in a cold bath 70 `of Water in FIGaZl and the metal is sealed as in FIG. 22.

In FIGURE 23 the anodized plate 71 with the water soluble pastes and color dyes 72 and 73 applied directly thereto as in FIG. l, but without any protective overcoating is placed in a chamber 74 and heated, as by the resistance element 75, to between 150 and 210 F. If the color pastes are still wet the moisture therein effects the transfer of the color into the pores of the metal, at least in part. Saturated steam is then admitted through the nozzle 76 to complete the color transfer to the metal as in FIG. 20. The metal pores may be sealed as in FIG. 22 or the steam in the chamber 74 may be maintained until the high temperature moisture seals the pores. Before the pore sealing temperature can penetrate the pastes 72 and 73, the color transfer will be complete. If the dye pastes are originally dry as will usually be the case if more than Ione color is applied, application of saturated steam for about l5 minutes will effect the dye transfer from the dry paste.

What is claimed as new is:

1. The process of coloring an aluminum surface which consists of anodizing the surface to provide a clean porous surface, providing `a water paste 'made up of solid-s taken from the class consisting of water soluble gums and starches which are relatively soluble in cold water and relatively insoluble in hot water, mixing a dye solvent which is miscible in water in said paste, mixing different colored dyes soluble in said solvent in separate batches of said paste and solvent mixture, applying coatings of said colored batches to different portions of said surface with Ione coating overlapping another in selected areas, allowing said coatings to dry to the touch, applying a protective coating of said uncolored paste over said colored coatings, immersing the surface so coated in a bath of water heated to between and 190 F. for a period of between 5 and 30 minutes to cause the colored dyes in said pastes to be transferred to the su'badjacent areas of said surface and mixed into a new color blend where the coatings overlap, immersing said surface in ll 1 water heated above 130 F. but below 200 F., removing said paper as soon as said quickly soluble coating has dissolved, leaving said metal with the` dye pastes and protective coating adhered thereto in said bath for over 5 Aminutes until the dyes from said pastes have transferred into the surface of said metal, removing said metal from said iirst bath and im-mersing it in a second bath heated above 200 F., to seal said anodized surface, and removing the residue of said colored pastes and said protective coating by flushing with water.

12. The process `of coloring an anodized aluminum surface which comprises the steps of providing a paper transfer sheet having a quickly water soluble coating on one face, applying a protective coating of an uncolored slowly water soluble 1but water permeable paste over said quickly soluble coating, applying multi-colored pastes of water soluble dyes to said protective coating and drying the colored pastes, adhering said paper by moisture with said colored pastes against the surface of the metal, dipping the metal with the paper adhered thereto in a rst bath of water heated above 130 but below 200 F., removing said paper las soon as said quickly soluble coating has dissolved, leaving said metal with the colored pastes and protective coating adhered thereto in said bath until the dyes from said pastes have transferred into the surface of said metal, removing said metal from said first bath and immersing it in a second bath heated above 200 F. to seal said anodized surface, and removing the residue of said colored pastes and said protective coating.

13. The process of coloring an anodized aluminum surface which comprises the steps of providing a transfer sheet having a quickly water soluble coating on one face, applying a protective coating of an uncolored slowly water soluble but Water permeable paste over said quickly soluble coating, applying multi-colored pastes impregnated with water soluble dyes to said protective coating and drying said pastes, adhering said sheet with said colored pastes against the surface of the metal, subjecting said metal and said sheet to moisture at elevated temperature, removing said paper as soon as said quickly soluble coating has dissolved, leaving said metal with the dye pastes and protective coating adhered thereto subject to said moisture until the dye from said paste has transferred into the surface of said metal, removing said metal from said moisture and immersing it in a bath heated above 200 F. to seal said anodized surface, and removing the residue of said colored pastes and said protective coating.

14. The process of coloring an anodized metal surface which comprises the steps of providing a transfer sheet with a protective coating of methylcellulose adhered to one side thereof by a layer of quickly water soluble adhesive, applying a colored design to said coating with a water soluble dye and permitting the dye to dry, applying the colored surface of said coating to said metal surface by moistening the meeting surfaces, subjecting said metal surface with said sheet adhered thereto to moisture heated above 130 but below 190 F. and removing said transfer sheet as soon as said layer of adhesive dissolves to cause color from said dye to transfer into the surface of said metal, and thereafter subjecting said metal surface to a temperature in excess of 200 F. to seal said surface and removing said methylcellulose coating and dye residue by flushing with water below 110 F.

15. The process of coloring an anodized metal surface which comprises the steps of providing a transfer sheet with a protective coating of methylcellulose adhered to one side thereof, applying a colored design to said coating with water soluble dye and permitting the dye -to dry, applying the colored surface of said coating to said metal surface, subjecting said metal surface with said sheet adhered thereto to moisture heated above 130 but below 190 F. to cause color from said dye to transfer into the surface of said metal, and thereafter subjecting said metal surface to a temperature in excess of 200 F. to seal said surface and removing said methylcellulose coating and dye residue.

16. The method of coloring an anodized metal surface in a predetermined pattern which comprises the steps of mixing a paste of methylcellulose in water below F., adding a water soluble dye to said paste, applying said colored paste to said surface in a predetermined design and allowing said paste to dry, dipping said metal surface with the paste applied thereto in water heated to above but below 200 F. to transfer dye from said paste to said surface, thereafter subjecting said metal to a temperature above 200 F. and removing said paste with cool water.

17. The method of coloring an anodized metal surface in a predetermined pattern which comprises the steps of mixing a paste of methylcellulose and water, adding a water soluble dye to said paste, applying said colored paste to said surface in a predetermined design, subjecting said metal surface with the paste applied thereto to moisture heated to above 130 F. but below 200 F. to transfer dye from said paste to said surface, thereafter subjecting said metal to a temperature above 200 F. and removing said paste with cool water.

18. The method of coloring an anodized metal sur- -face in a predetermined pattern which comprises the steps of mixing a paste of methylcellulose and water, adding a water soluble dye to said paste, applying said colored paste to said surface in a predetermined design and allowing said paste to dry, heating said surface and paste to between F. and 210 F., subjecting said metal surface so heated with the paste applied thereto to moisture at a temperature above 130 F. to transfer dye from said paste to said surface, thereafter subjecting said metal to moisture Vat a temperature above 212 F. and removing said paste with cool water.

19. The method of coloring an anodized metal surface in a predetermined pattern which comprises the steps of mixing a paste of water soluble dye and a water permeable binder, bringing said colored paste and said surface into contact in a predetermined design under heated condition of said surface at between 150 F. and 210 F. and wet condition of said paste to transfer dye from said paste to said surface, thereafter subjecting said metal to a temperature above 200 F. to seal said surface and removing said paste.

20. The method of coloring an anodized aluminum surface which comprises the steps of preparing a transfer sheet of metal foil with a quickly water soluble coating on one face, depositing a slowly water soluble paste impregnated with a water soluble dye in a predetermined design on said coating, applying and adhering said sheet with said paste against said surface with water paste, removing said sheet as -said adhering Water paste dissolves said coating, heating said surface with said paste thereon to between 150 F. and 210 F., subjecting the opposite side of said paste from said surface to water vapor above 200 F., and thereafter subjecting said surface to moisture -at sealing temperature and removing said paste.

21. The method of coloring an anodized aluminum surface which comprises the steps of preparing a transfer sheet of metal foil with a quickly water soluble coating on one face, depositing a water permeable paste impregnated with a water soluble dye in a predetermined design on said coating, applying and adhering said sheet with said paste against said surface with water applied between said aluminum surface and the paste on said sheet, removing said sheet .as said adhering water dissolves said coating, heating said surface with said paste thereon to between 150 F. and 210 F., subjecting the opposite side of said paste from said surface to water vapor .above 200 F., and thereafter subjecting said surface to moisture at sealing temperature and removing said paste.

9 a bath of water wtih nickel acetate therein at a temperature 200 and 212 F. to seal said porous surface, and mechanically removing said coatings from said surface.

2. The process of coloring an aluminum surface which consists of anodizing the surface to provide a clean porous surface, providing a water paste made up of solids taken from the class consisting of water soluble gums and starches 'that are relatively soluble in cold water and relatively insoluble in hot water, mixing different colored dyes soluble in water in separate batches of said paste, applying coatings of said colored batches Vto different portions of said surface, allowing said coatings to dry to the touch, applying a protective coating of said uncolored paste over said colored coatings, immersing the surface so coated in a bath of water heated to between 130 and 190 F. for a period of between 5 and 30 minutes to cause the colored dyes in said pastes to be transferred to the subadjacent areas of said surface, immersing said surface in a bath of water at a temperature between 200 and 212 F. to -seal said porous surface, and mechanically removing said coatings from said surface.

3. The process of coloring yan aluminum surface which consists of anodizing the surface to provide a clean porous surface, providing an adhesive water paste made up of solids that are relatively -soluble in cold water and reladyes soluble in said paste in separate batches of said paste,

lapplying `coatings of said colored batches to different p 'portions of said surface with overlapping of the colors in selected areas, allowing said coatings to dry to the touch, applying a protective coating of said uncolored paste over said colored coatings, immersing the surface s-o coated in -a bath of water heated to between 130 and 190 F. for a period of between 5 and 30 minutes to cause the color dyes in said pastes to be transferred to the subadjacent areas of said surface with blending of the colors in`said overlapped areas, immersing said surface in a bath of water at a temperature between 200 and 212 F. to seal said porous surface, and mechanically removing said coatings from said surface.

`4. The process of coloring an aluminum surface which consists of anodizing the surface to provide a clean porous surface, providing an adhesive paste which is relatively insoluble in hot water but water permeable, mixing different colored dyes soluble in said paste in separate batches yof said paste, applying coatings of said colored batches to different portions of said surface, allowing said Coatings to dry to the touch, applying a protective coating of a water permeable but relatively water insoluble material over said colored coatings, immersing the surface so coated in a bath `of water heated to between 130 and 190 F. for a period of between 5 and 30 minutes to cause the color dyes in said pastes to be transferred to the subadjacent areas of said surface, irnmersing said surface in a bath of water at a temperature between 200 and 212 F. to seal said porous surface, and dissolving said coatings from said surface.

5. The process of coloring an unsealed anodized aluminum surface which consists lof the steps of applying a multicolor design to the unsealed anodized surface by means of plural colored dye impregnated water pastes arranged in touching and overlapping relation in parts, applying a protective coating over said pastes, immersing the metal so coated in a bath of water heated above 130 F. but below 200 F. for 5 to 30 minutes to transfer the dye from the paste to the metal, immersing the metal in a bath of water heated above 200 F. -for a minimum of minutes to seal the anodized surface, and removing residue of said paste and coating, said protective coating being insoluble in said first bath during the period of the bath but being water permeable, the dyes in said pastes being water soluble.

6. The process of coloring an unsealed anodized aluminum surface which consists of the steps of applying a multicolor design to the unsealed anodized surface by means of plural colored dye impregnated water pastes, applying a protective coating over said pastes, immersing the metal .so coated in a bath of water heated above F. but bel-ow 200 F. for 5 to 30 minutes to transfer the dye from the pastes to the metal, immersing the metal in a bath of water heated above 200 F. for a minimum of 5 minutes to seal the anodized surface, and then removing residue of said pastes and coating, said protective coating being insoluble in said first bath during the period of the bath but being water permeable.

7. The process of coloring an unsealed anodized aluminum surface which consists of the steps of applying a multicolor design to the unsealed anodized surface by means of plural colored dye impregnated water pastes, applying a protective coating over said pastes, immersing the metal so coated in a bath of water heated above 130 F. `but |below 200 F. for 5 t-o 30 minutes to transfer the dye from the pastes to the metal, immersing the metal in a =bath of water heated above 200 F. for a minimum of 5 minutes to seal the anodized surface, and then removing residue of said pastes and coating, said protective coating being insoluble in said first bath during the period of the bath but being water permeable, the dyes in said pastes being soluble in solvents miscible with water.

8. The process of coloring an unsealed anodized aluminum surface which consists of the steps of applying plural dye impregnated water pastes including a binder that is slowly soluble in hot water to said surface, dipping said surface with the pastes applied thereto in a bath of water heated to above 130 but below 200 F. while retaining said pastes against dispersion in said water by said binder, dipping said surface in a second bath of water heated above 200 F. to seal said surface, and removing residue of said pastes and said binder.

9. The pro-cess of coloring an unsealed anodized aluminum surface which consists of the steps of applying a dye impregnated water paste to said surface, dipping said surface with the paste applied thereto in a bath of water heated to above 130 but below 200 F. while retaining said paste against dispersion in said water by a binder adhered to the surface and insoluble in water during the period of said dip, dipping said surface in a second bath of water heated above 200 F. to seal said surface, and removing residue of said paste and said binder.

10. The method of coloring an anodized metal surface which comprises applying dye impregnated paste to said surface in a preselected design, holding said paste in position on said surface by a material insoluble in hot water but permeable to hot water, ydipping said surface with said paste so held in place thereon in a bath of water heated to over 130 but below 200 F. to cause the hot water to permeate said material and transfer color from said paste ot said surface, thereafter subjecting said surface to a temperature in excess of 200 F. to seal said surface and removing residue of said paste and said holding material.

111. The process of coloring an anodized aluminum surface which comprises the steps of providing a paper transfer sheet having a quickly water soluble coating on one face, applying a protective coating of an uncolored slowly water soluble but water permeable paste over said quickly soluble coating, applying multi-colored pastes of water soluble dyes to said protective coating with overlapping of the colored pastes in selected areas, allowing said protective coating to dry, adhering said paper with said colored pastes vagainst the surface of the metal by applying a line of moist adhesive between the metal and one edge of the sheet and progressively pressing the sheet against the metal to expel air and advance they adhesive between the converging paper and metal, dipping the metal with the paper adhered thereto in a first bath of 22. The method of coloring an anodized valuminum surface which comprises the steps of depositing la paste impregnated with a water soluble dye on said surface in a predetermined design by transfer from a carrier sheet bearing the paste in the said design, heating said surface with said paste thereon to between 150 F. and 210 F., subjecting the opposite side of said paste from said surface so heated to saturate steam for about 15 minutes to transfer the dye from the paste to said surface, and thereafter sealing said 4surface and removing the residue of said paste.

23. The method of coloring an anodized aluminum surface which comprises the steps of depositing a paste impregnated with a water soluble dye on said surface in a predetermined design, heating said surface With said paste 4thereon to between 150 F. and 210 F., subjecting the opposite side of said paste from said surface so heated to saturate steam for about 15 minutes to transfer the dye from the paste to said surface, and thereafter sealing said surface and removing the residue of said paste.

24. The method of coloring an anodized surface of aluminum which comprises the steps of heating said surface to between 150 F. and 210 F., applying a paste im lpregnated with a water soluble dye in a predetermined pattern to said surface while so heated by printing said paste on said surface, and thereafter sealing said surface and removing the residue of said paste.

25. The method of coloring an anodized surface of aluminum which comprises the steps of heating said surface to between 150 and 210 F., applying paste impregnated with a water soluble dye in a predetermined pattern to said surface while so heated, and thereafter sealing said surface and removing the residue of said paste.

26. A decalcomania for coloring an anodized aluminum surface comprising a paper transfer sheet having a quickly water soluble first coating on one face, a sec-ond coating of a water soluble paste taken from the class consisting of Water soluble gums, starches and plastics, and multicolored water soluble pastes applied to said second coating with overlapping of the colored pastes in selected areas, said second coating being an uncolored slowly water soluble but water permeable paste of the same base as said colored pastes.

27. A decalcomania for coloring an anodized aluminum surface comprising a paper transfer sheet having a quickly water soluble first coating on one face, a second coating of a water soluble paste taken from the class consisting `of water soluble gums, starches and plastics, and multicolored water soluble pastes applied to said second coating with overlapping of the colored pastes in selected areas, said second coating being an uncolored slowly water soluble but water permeable paste.

28. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet having a quickly water soluble first coating on one face, a protective second coating of an uncolored slowly water soluble but water permeable paste Vover said quickly soluble coa-ting, and multicolored water soluble pastes on different selected areas of the exposed surface of said protective coating.

29. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet having a quickly water soluble first coating on one face, a protective second coating of a slowly water soluble but water permeable paste over said quickly soluble first coating, and water soluble colored paste applied to selected areas of the exposed surface of said protective Icoating, said second coating being devoid of soluble dye.

30. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet, a protective coating of a slowly wa-ter soluble but water permeable material on said sheet, and water soluble dye applied to selected areas of the exposed surface of said coating, said coating being devoid of soluble dye.

31. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet, a protective coating of a slowly water soluble but water permeable material on said sheet, and a dye soluble in a solvent miscible in water applied to selected areas of the exposed surface of said coating, said coating being devoid of soluble dye.

32. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet having a quickly water soluble first coating on one face, a protective second coating of methycellulose over said quickly soluble first coating, and water soluble dye applied =to selected areas of the exposed surface of said methylcellulose, said second coating being devoid of soluble dye.

33. A decalcomania for coloring an anodized aluminum surface comprising a transfer sheet having a protective coating of methylcellulose, and water soluble dye applied to selected areas of the exposed surface of said methycellulose coating, said coating being devoid of soluble dye.

34. A decalcomania for coloring an anodized aluminum surface comprising, a transfer sheet having different colored pastes applied at different selected areas of one surface thereof, said pastes comprising dyes and materials that are slowly soluble in hot water but water permeable, the different colors of said pastes being formed by dilerent colored dyes that are soluble in water and impregnated through said pastes.

References Cited by the Examiner UNITED STATES PATENTS 1,759,868 5/1930 Sadtler 8-2.5 1,797,947 3/ 1931 Sadtler 8-2.5 2,614,912 10/1952 Rice 204-38 X 2,629,670 2/ 1953 Rathke 154-99 X 2,778,790 1/1957 Sobol 204-35 X W. VAN SISE, Assistant Examiner.

JOHN H. MACK, Primary Examiner. 

1. THE PROCESS OF COLORING AN ALUMINUM SURFACE WHICH CONSISTS OF ANODIZING THE SURFACE TO PROVIDE A CLEAN POROUS SURFACE, PROVIDING A WATER PASTE MADE UP OF SOLIDS TAKEN FROM THE CLASS CONSISTING OF WATER SOLUBLE GUMS AND STARCHES WHICH ARE RELATIVELY SOLUBLE IN COLD WATER AND RELATIVELY INSOLUBLE IN HOT WATER, MIXING A DYE SOLVENT WHICH IS MISCIBLE IN WATER IN SAID PASTE, MIXING DIFFERENT COLORED DYES SOLUBLE IN SAID SOLVENT SEPARATE BATCHES OF SAID PASTE AND SOLVENT MIXTUER, APPLYING COATINGS OF SAID COLORED BATCHES TO DIFFERENT PORTIONS OF SAID SURFACE WITH ONE COATING OVERLAPPING ANOTHER IN SELECTED AREAS, ALLOWING SAID COATINGS TO DRY TO THE TOUCH, APPLYING A PROTECTIVE COATING OF SAID UNCOLORED PASTE OVER SAID COLORED COATINGS, IMMERSING THE SURFACE SO COATED IN A BATH OF WATER HEATED TO BETWEEN 130* AND 190*F. FOR A PERIOD OF BETWEEN 5 AND 30 MINUTED TO CAUSE THE COLORED DYES IN SAID PASTES TO BE TRANSFERRED TO THE SUBADJACENT AREAS OF SAID SURFACE AND MIXED INTO A NEW COLOR BLEND WHERE THE COATINGS OVERLAP, IMMERSING SAID SURFACE IN A BATH OF WATER WITH NICKEL ACERATE THEREIN AT A TEMPERATURE 200* AND 212*F. TO SEAL SAID POROUS SURFACE, AND MECHANICALLY REMOVING SAID COATINGS FROM SAID SURFACE. 